A variable-sweep wing is a wing of an aircraft, missile or unmanned vehicle that is capable of being swept back, i.e., rotated with respect to the fuselage of the vehicle, in flight or while stationary. In use, the wing is swept back for storage, carriage, and/or cruising at high speeds; while the wing is unswept for flight operation, specifically at low speeds, takeoff and landing. The variable-sweep wing has been used primarily in military vehicles for performance enhancement and/or storage and carriage considerations.
Several variable-sweep wing configurations are known. In a twin-pivot configuration, the wings of an aircraft pivot about their individual pivot axes. F-14 and F-111 aircrafts incorporate twin-pivot style wings, for example. The aircraft wing beam structure is interrupted by two pins which are joined by a structural box. When swept, the wing beam structure cannot completely overlap because the pins are separated by a pre-determined axial distance, spanwise, across the fuselage.
In a single pivot oblique configuration, such as that disclosed in U.S. Pat. No. 4,132,374, which is incorporated by reference herein, an oblique wing is provided in the form of a continuous beam mounted to the aircraft. The asymmetric nature of deploying an oblique wing in flight introduces aerodynamic imbalances that may be problematic for flight control during wing extension.
In a single-point pivot concentric shaft configuration, a single-point pivot concentric shaft pivots two wings about a single axis. The concentric shafts penetrate the fuselage and are relatively complex to operate and manufacture.
Variable-sweep wings may include a flexible membrane that is inflated or extended by an articulating skeleton to sweep the wings. Such a flexible membrane may lack structural integrity or be perceived to lack structural integrity, as compared with rigid wings.
While several variable-sweep wing configurations are known, there is a continuing need to develop and improve upon variable-sweep wings in the interest of structural integrity, performance and cost, for example.